[willamette-fcst] Forecast - Tuesday, November 3rd, 2009

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Tuesday, November 3rd, 2009 at 9:00am.

Burn Advisory:
     Agricultural burning is not recommended.
     Stack burning is not allowed.

Weather Discussion:
     An upper-level ridge of high pressure will slowly build over
     Oregon and Washington today...pusing the jet stream
     northward, into southern British Columbia.  Infrared
     satellite imagery showed considerable high and mid-level
     clouds streaming across both states this morning, via a
     westerly flow aloft.  The ODA surface analysis showed high
     pressure centered over northeastern Oregon, with a thermal
     trough building northward along the southern Oregon Coast. 
     That was increasing the northeasterly pressure-gradients
     across western Oregon.

     The Salem sounding this morning showed a significant
     low-level temperatures inversion, with surface temperatures
     in the 30s and 3000-foot temperatures near 50 degrees.  East
     winds between 10 and 20 mph were dropping off of the coastal
     range and keeping fog off the beaches.  Northerly winds had
     not developed enough yet to rid the Willamette Valley of
     morning fog, which was locally reducing visibilities to 1/4
     mile or less.  Mid-morning temperatures ranged from the mid
     30s, in the foggy Willamette Valley, to near 50, with mid
     only middle and high clouds, along the coast.

     Increasing low-level offshore flow will continue to dry out
     the air mass today, with the building upper-level ridge
     further warming temperatures aloft.  Morning valley fog
     should give way to filtered sunshine this afternoon, across
     the Willamette Valley, with temperatures climbing to around
     60 degrees or higher.  Sections of the coast range and
     Cascade foothills should reach the mid 60s, due to the very
     mild air aloft.  Much of the coastline will also climb into
     the low to mid 60s today, due to the drying and warming
     influence of the offshore downsloping winds.  Low mixing
     heights will make for poor ventilation conditions again
     today across the Willamette Valley.

Surface Winds:
     NNE 5-15 this morning, NNE 5-15 this afternoon.
Transport Winds:
     NE 12 this morning, NE 12 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 1300 feet.  Ventilation index 16.
High Temperature:
     Salem\'s high temperature today will be near 60.
Humidities:
     Minimum relative humidity will be near 46%.
Sunrise/Sunset:
     Salem sunset tonight: 4:57pm; sunrise tomorrow: 6:55am.

Extended Outlook:
     The upper-level ridge of high pressure is forecast to shift
     eastward Wednesday, to over Idaho and Montana.  At the
     surface, easterly outflow, from the Columbia Gorge, will
     likely keep fog out of much of the Portland area Wednesday
     morning, but it should reform across the central and
     southern Willamette Valley.  Areas of morning valley fog
     will give way to high and mid-level clouds, in the
     afternoon, with increasing southwesterly flow aloft over
     Washington and Oregon. Valley highs should climb above
     normal again Wednesday afternoon.

     The ridge is forecast to continue eastward on Thursday, with
     the first of several wet weather systems forecast to come
     onshore by the afternoon.  The cold front is forecast to
     push east of the region Friday morning, with the steady rain
     turning showery.  Snow levels will drop to around to Cascade
     passes.  The next system is forecast to come onshore
     Saturday, followed by an even colder upper-level trough on
     Sunday.  Yet another system is forecast to come onshore Monday.

Tomorrow (04 Nov):  Areas of AM Fog and Low Clouds.  Filtered Afternoon Sunshine.  36/63

Thu (05 Nov):  Increasing Clouds.  Rain Developing by Afternoon.  40/60

Fri (06 Nov):  Rain Turning to Showers.  Snow Level Dropping to 4-5000 feet.  48/54

Sat (07 Nov):  Rain.  Snow Level 4-5000 Feet.  44/51

Sun (08 Nov):  Decrasing Showers.  Snow Level 3-4000 Feet.  42/52

Mon (09 Nov):  Rain Developing.  Snow Level 4-5000 Feet.  40/53

Tue (10 Nov):  Showers.  Snow Level 3-4000 Feet.  40/54

ODA Meteorologist
weather at oda.state.or.us